A molar pregnancy occurs when the fertilisation of the egg by the sperm goes wrong and leads to the growth of abnormal cells or clusters of water filled sacs inside the womb. This condition is one of a group of conditions known as gestational trophoblastic tumours (GTTs). Molar pregnancies used to be called hydatidiform mole but now most people call them molar pregnancies. Most molar pregnancies are benign (not cancerous). They can spread beyond the womb in some women, but are still curable.
In the past GTD was often fatal. However, medical advances in the past 50 years mean that the disease is now invariably curable. Almost 100% of patients with benign tumours, or metastatic tumours are successfully cured and most women retain their fertility following treatment. Transvaginal and transabdominal ultrasound are also commonly used diagnostic tools, which enable doctors to see signs of molar pregnancy. The doctor will take an ultrasound of the areas likely to be affected if a molar pregnancy is in fact occurring, and examine the ultrasonic images for evidence of GTD.
All women of reproductive age who have previously been, or are currently pregnant, are at risk of GTD, however women younger than 16 or older than 40 who become pregnant are more likely than women aged 16-39, to develop a molar pregnancy. An estimated 1-3 in 1000 pregnancies are affected by benign hydatidiform moles; however incidence varies internationally and is highest in the Asian region. Some 10% of all hydatidiform moles will become malignant; an estimated 8-15% of complete and 1.5-6% of partial hydatidiform moles.